1. Field of Invention
The present invention relates to street sweepers and, more particularly, to non-motorized, towable sweeping apparatus for collecting dirt and debris upon its conveyance over a surface to be swept.
2. Technical Considerations
Advancements in the art of street sweeping apparatus are characterized and embodied in patents spanning more than a century. The original mechanized models were the non-motorized versions, necessitated by the early state of the art. Incumbent upon the inventors of the 1800's was a street sweeping machine utilizing "horse power" in its strictest sense. Such machines utilized the rotation of the ground surface engaging wheels to drive the sweeping brushes in the sweeping operation. Such a sweeper is disclosed in U.S. Pat. No. 35,365, issued to Daboll in 1862, wherein a cylindrically shaped brush was operated through the engagement of rigid frictional drive rollers for the collection of dirt and debris in bin storage areas formed within the sweeping unit housing.
Advancements in the sweeping art were consistent with those of a mechanized society. Chain drives, gears, and pall and ratchet combinations were introduced in an effort to achieve a sweeping unit design which could be built, maintained, and operated economically with great effectiveness. With the advent of the internal combustion engine, such units became "self-powered" and therefore relatively complex and costly. But as complexity increased, so did problems in operation and maintenance. Debris and unwanted materials, although the object of the sweeping operations, formed abrasives often interfering with the myriad of moving parts in the self-powered sweeping unit.
The self-powered units proved to be most effective in large scale sweeping operations. However, due to the overall size of such units, they were impractical for smaller industrial uses where the several cleaning locations were spread apart. Physically and economically it proved to be impractical to transport large, self-powered sweepers for relatively small cleaning jobs.
As more recent patents illustrate, sweeper attachments have therefore been provided for lift trucks and similar motorized vehicles particularly adapted for the pushing or pulling of the attachment over the surface to be swept. Such vehicles are often located at industrial sites for other, unrelated uses.
Some of the advancements in attachable sweepers utilized the developments of the early art in direct wheel to brush drive rotational interengagement. For example, the U.S. Pat. No. 3,354,489 issued to S. V. Ehrlich on Nov. 28, 1967, discloses a sweeper attachment for a lift truck. This and other similar sweeping machines incorporate drive wheel transmissions, one way over-riding clutches, enclosed bin areas adjacent the brush and means for engaging the unit for lifting it to deposit the debris within. These units further include features such as floating steering, and a method of attachment utilizing the adaptation of all makes and models of lift trucks.
It has been recognized that the use of lifting forks, as used on fork lifts, greatly facilitates the elimination of debris and waste in attachable sweeping units, by the elevation of same above a refuse container for discarding such dirt and debris. However, the impracticality of using such a fork lift device for the complete sweeping operation has likewise been recognized. The general concept of using a sweeping apparatus with a trash bin, which can be towed behind any variety of motorized vehicles such as pick-up trucks thus becomes an optimal design goal.
The fullest utilization of the state of the art has not been recognized in the development and reduction to practice of modern sweeping concepts. The frictional engagement-type transmissions have consistently used rigid drums for drive capstans, having outer peripheries with serrated surfaces to improve friction thereon. The expense of such designs is complicated by the problem of wear, adjustment in the magnitude of frictional engagement, and susceptibility to abrasives encountered in the sweeping operation. Complicated and expensive adjustment mechanisms, linkages, and contamination precautions are often provided or else separate drive systems such as hydraulic or chain drive take offs are incorporated. Such systems are designed around these problems rather than attempting to deal with them.
Frictional drive transmissions require merely two engaging drive surfaces having a suitably high coefficient of friction. The engaging drive elements, by necessity, must be compatible, whether wet or dry, of economical construction, suitably maintenance free, relatively impervious to dirt, debris and other abrasives encountered in the sweeping operation and provide a means for adjustment of normal force and size of the contiguous peripheral portions.
Heretofore sweeping apparatus has been unavailable for the brushing and cleaning operations above described with the simplicity of construction, economic features, and other advantages over the prior art. With the growing demand for maintenance and cleaning of segregated paved surfaces due to the widespread placing of same, the need has been fostered for the construction of such a sweeping unit. This need, as well as the requirements of conservation of energy and control of economy has necessitated the creation of an improved brushing and sweeping apparatus.